For example, in a portable terminal such as a cell phone, the connecting part of a hard circuit board is coupled to the connecting part of a soft circuit board in an enclosure. The connecting parts of these circuit boards are shown in FIG. 9.
A first circuit board 100 includes a mounting part 102 where numerous electronic components are mounted along the surface of a soft base material 101 and a connecting part 104 where a plurality of circuit patterns 103 are arranged in parallel adjacent to the mounting part 102, the mounting part 102 covered with a resist or a coverlay.
A second circuit board 106 includes a mounting part 108 where numerous electronic components are mounted along the surface of a hard base material 107 and a connecting part 110 where a plurality of circuit patterns 109 are arranged in parallel adjacent to the mounting part 108, the mounting part 108 covered with a resist or a coverlay.
To connect the first circuit board 100 and the second circuit board 106 to each other, respective connecting parts 104, 110 are opposedly disposed via an adhesive, and the connecting parts 104, 110 are pinched by the upper mold 113 and lower mold 114 of a pressurizing jig 112 thus subjected to hot pressure welding.
The first circuit board 100 and the second circuit board 106 are fixed together while the adhesive extruded from between the opposed circuit patterns 103, 109 under hot pressure welding bonds the soft base material 101 and the hard base material 107 to each other and the circuit patterns 103, 109 on the connecting parts 104, 110 are thus in face contact to each other.
On the first circuit board 100, the mounting part 102 and the connecting part 104 are arranged in an L shape in displaced positions from each other rather than a belt shape where the mounting part 102 and the connecting part 104 are arranged in a linear shape in order to support a compact, lower-profile enclosure design.
Similarly, on the second circuit board 106, the mounting part 108 and the connecting part 110 are arranged in an L shape in displaced positions from each other rather than a belt shape where the mounting part 108 and the connecting part 110 are arranged in a linear shape in order to support a compact, lower-profile enclosure design.
Thus, as shown in FIG. 10, when the first circuit board 100 and the second circuit board 106 are connected to each other, the heat in a section 116 of the connecting parts 104, 110 subjected to hot pressure welding that is close to the hard base material 107 is transmitted as shown by an arrow A. On the other hand, the heat in a section 117 distant from the hard base material 107 is unlikely to be transmitted as shown by an arrow B. Thus, the section 117 distant from the hard base material 107 is likely to confine heat.
In this example, heat is unlikely to be transmitted to the soft base material 101 and is likely to be transmitted to the hard base material 107.
In this case, the heat transmitted to the connecting parts 104, 110 are uneven, thus causing a temperature difference between the section 117 distant from the hard base material 107 and the section 116 close to the hard base material 107.
That is, the section 117 distant from the hard base material 107 is a high-temperature section while the section 116 close to the hard base material 107 is a low-temperature section.
As a result, the soft base material 101 may be excessively softened in part and is unnecessarily drawn by pressurization. This may lead to displacement of the circuit patterns 103, 109 in the high-temperature section 117 (refer to FIG. 9) or failure to obtain necessary bonding strength due to uneven hard bodies in the adhesive.
To solve the problems, there has been proposed a method for manufacturing a liquid crystal display device for keeping at room temperatures or cooling the surface of one mold out of a pair of molds 113, 114 constituting a pressurizing jig 112 (refer to FIG. 9) (see Patent Reference 1).    [Patent Reference 1] JP-A-11-7040